Reductions of manufacturing yield in the manufacturing process of semiconductor devices have a direct effect in increasing the product's costs, so that the improvement of manufacturing yield has become an important challenge. One of the main factors leading to a decrease in manufacturing yield is the adherence of foreign matter to the semiconductor substrate, so that there is a strong demand for a technology for detecting the state of adherence of foreign matter efficiently and with high sensitivity.
Conventionally, it is well known to use optical means as a technology for detecting foreign matter on a semiconductor substrate. FIG. 9 is a schematic diagram showing a configuration example of a conventional surface foreign matter inspection device using optical means. In FIG. 9, the conventional surface foreign matter inspection device includes an optical system (radiation optical system (ROS) 5, detection optical system 12), and a control processing system (stage 4a, optical detection means (PDM) 6, information processing device 100). Ordinarily, a laser is used for the radiation optical system 5. The detection optical system 12 is composed of condensing lenses 2 and an optical filter 7a, and focuses light scattered by foreign matter on the semiconductor substrate.
Using this device, foreign matter on a silicon wafer 4 can be inspected as follows. Laser light is irradiated from the radiation optical system 5 onto the silicon wafer 4, which is placed on the stage 4a. Then, when foreign matter is present at the location onto which the laser light is irradiated, the reflected light that is scattered by this foreign matter is captured in the detection optical system 12, condensed by the detection optical system 12, and the condensed light is converted into an electrical signal by the optical detection means 6. By processing this electrical signal with the information processing device 100, and by also processing information about the position of the foreign matter on the silicon wafer 4 in the information processing device 100, foreign matter on the silicon wafer 4 can be inspected. In the surface foreign matter inspection device using such optical means, in order to detect foreign matter of even tinier size with high sensitivity, the intensity of the irradiated light is enhanced, the sensitivity of the optical detector 6 is enhanced, or the focusing ability of the optical system is improved.
If the detection optical system 12 composed of ordinary optical elements as shown in FIG. 9 is used, then increasing the NA (numerical aperture) of the optical system in order to improve its focusing ability leads to the problem that the size of the detection optical system 12 becomes large, resulting in interference with light irradiated from the radiation optical system 5.
On the other hand, when an optical element of an optically reflective system, for example a parabolic mirror, is used for the detection optical system 12, then reflected light can be captured over a broad scanning range on the object under inspection while avoiding interference with the irradiated light due to the relatively small size of the detection optical system 12.
However, with such a detection optical system, the region over which the reflected light can be captured without aberrations is restricted to one point on the optical axis of the parabolic mirror, so that the object point range on the object under inspection over which the detection optical system can capture the reflected light, becomes narrow, and as a result, the scanning range of the radiation optical system on the object under inspection becomes small. Thus, the amount of scanning by the radiation optical system over the object under inspection becomes very large, and a long time is needed to inspect for foreign matter.
It is thus an object of the present invention to solve these problems of the prior art and to provide a surface foreign matter inspection device, with which the NA of the optical system can be enlarged with a simple configuration, and the shortening of the time required for foreign matter inspection as well as a high detection sensitivity can be achieved.